How do you get dual tainted claymore of miltonius?

You need 13 diamonds of miltonius, 13 tainted gems, and 13 dark crystal shards. You also need the contract of Miltonius(unidentified 13) and the voucher of miltonius(non-mem)

You need to get to miltonius which requires:
okoduro's tooth
hydra scale
50 killed makai
escherion's chain
strand of vath's hair
arcara's fang

It is a combat style quest.

You can get the diamonds from a new drudgen quest
you can turn in 1 contract of miltonius for 3 diamonds.